Mr Livingstone is a major supporter of Labour leader Jeremy Corbyn and was recently appointed co-covener of the party’s policy review on defence amid a major row internal row over renewing the Trident nuclear missile.

Mr Corbyn today put pressure on his MPs by telling them he would not support the Prime Minister’s case to launch targeted bombing raids on ISIL extremists in Syria, a cause which has intensified since the Paris terrorists attacks.

MPs could vote on Britain’s involvement next with huge uncertainty over whether the PM has enough support.

On Question Time, Mr Livingstone was asked why he would not support the airstrikes, which are already being led by the US and France.

He said: "Bombing on its own isn’t enough. We shouldn’t get caught up in that again. I remember when Tony Blair was told by the security services if you go into Iraq we will be a target for terrorism. He ignored that advice and it killed 52 Londoners.”

Mr Livingstone went on to warn of the risks to tackling terrorism at home of cutting neighbourhood policing.

Ken Livingstone: "They gave their lives. They said what they believed."

He was swiftly challenged by Mr Forde, who formerly worked for the Labour Party and tore up his membership after Mr Corbyn’s election.

The comedian said: "The idea you can absolve those people who killed innocent Londoners by blaming Tony Blair is shameful."

But Mr Livingstone replied: "Well, you can go and look at what they put on their website. They did those killings because of our invasion of Iraq."

Mr Forde again rebutted: "So you accept the propaganda of the terrorists, Ken?"

Mr Livingstone replied again: "They gave their lives. They said what they believed. They took Londoners’ lives in protest against our invasion of Iraq. We were lied to by Tony Blair. There was no weapons of mass destruction.”

Mr Livingstone repeated: "If we had not invaded Iraq those four men would not have gone out and killed 52 Londoners. We know that - I saw the police intelligence report.”

The tone contrast to the impassioned, hugely-respected speech he made as London struggled to comprehend the violence on 7 July 2005 where he warned the attackers: "Whatever you do, however many you kill, you will fail".

The then-mayor of London had been in Singapore celebrating the city securing the 2012 Olympics when the bombs exploded at four sites in London. One section won particular praise:

This was not a terrorist attack against the mighty and the powerful. It was not aimed at Presidents or Prime Ministers.

It was aimed at ordinary, working-class Londoners, black and white, Muslim and Christian, Hindu and Jew, young and old. It was an indiscriminate attempt to slaughter, irrespective of any considerations for age, for class, for religion, or whatever.

That isn't an ideology, it isn't even a perverted faith - it is just an indiscriminate attempt at mass murder and we know what the objective is. They seek to divide Londoners. They seek to turn Londoners against each other.

I said yesterday to the International Olympic Committee, that the city of London is the greatest in the world, because everybody lives side by side in harmony. Londoners will not be divided by this cowardly attack. They will stand together in solidarity alongside those who have been injured and those who have been bereaved and that is why I'm proud to be the mayor of that city.